Accelerator system for crosslinking polymers which harden on exposure to the moisture in air

ABSTRACT

An accelerator system for the cold crosslinking of polymers which harden on exposure to moisture by hydrolysis/condensation, comprising: (C) x parts by weight of a catalyst for crosslinking the said polymers by polycondensation, x ranging from 0.01 to 10; (E) Y parts by weight of a solid inorganic compound containing an amount y of water in the form of water of hydration and/or water adsorbed by capillary condensation, this amount y ranging from 0.5 to 40 parts by weight, and which can represent up to 70% of the weight of the said solid inorganic compound; (F) z parts by weight of fillers, z ranging from 0 to 50; (D) 100-(x+Y+z) parts by weight of a diluent or of a solvent of the said catalyst (C), the diluent or solvent having a dynamic viscosity at 25° C. of the order of 50 to 200,000 mPa.s; the respective amounts of the four constituents (C), (E), (F) and (D) being such that the system obtained exists in the form of a manipulable paste. The accelerator system is used for accelerating silicone compositions which harden on exposure to the moisture in air.

The subject of the present invention is a new accelerator system forcrosslinking polymers which harden on exposure to moisture by apolycondensation reaction and the use of the said system for themanufacture of so-called "neutral" adhesives and mastics by coldcrosslinking of polyorganosiloxanes containing alkoxysilyl orketiminoxysilyl functional groups.

Single-component silicone compositions used as mastics or adhesivescrosslink while cold according to a mechanism of hydrolysis of reactivefunctional groups of acetoxysilane, ketiminoxysilane or alkoxysilanetype or the like, followed by condensation reactions between silanolgroups formed and other residual reactive functional groups. Hydrolysisis generally carried out by virtue of water vapour which diffuses intothe material from the surface exposed to the atmosphere. When thethickness of the said material is large, the time required to crosslinkthe unexposed face can be significant; thus, it generally requires morethan 100 hours to crosslink a seal with a thickness of 10 mm.

In certain applications, such as, for example, technical mastics forinsulating glazings or bondings for automobile components, it isimportant to have available a rapid-setting material.

It has been proposed to add hardening accelerators to acetoxy (andgenerally acyloxy) silicone compositions which crosslink while cold,especially hardening accelerators of the type:

anhydrous or hydrated alkali metal or alkaline-earth metal phosphates,to be added at the time of use (U.S. Pat. No. 4,508,888);

alkali metal or alkaline-earth metal hydroxides, to be added at the timeof use (U.S. Pat. No. 4,532,315); the most efficient systems arealkaline-earth metal hydroxides, in particular lime, which reacts withthe acetic acid released by the silicone composition, giving water andsodium acetate; the water produced by the reaction leads to thehydrolysis of the acetoxy functional groups, which brings about theformation of twice as much acetic acid as at the start; the reactionthus continues in self-accelerating; the setting can thus be very fast.

hydrogels based on organic polymers swollen with water, and added at thetime of use (U.S. Pat. No. 4,918,121). It has also been proposed(EP-A-372,347) to accelerate acetoxy silicone compositions by additionof a system based on an emulsion of water in a silicone oil. The use isalso known (British Patent 1,308,985) of molecular sieves to control therate of crosslinking of acetoxy silicone elastomer compositions.

There are fields of application where neutral hardenable siliconecompositions (that is to say, non-acyloxy) are preferred to acidiccompositions (that is to say, acyloxy); this is especially the case asregards the production:

of coatings on metals such as iron, zinc, copper and the like or ontreated glasses, which corrode on contact with acids;

of coatings on concrete, where the formation of blooming is observed;

of seals for housings containing electronic equipment which is sensitiveto acids.

In all these applications, it may be advantageous to have availablerapid-setting neutral hardenable silicone compositions.

It was observed that increasing the amount of catalyst in neutralhardenable silicone compositions only has a small amount of influence onthe in-depth crosslinking rate. On the other hand, the addition of freewater to the formulation causes a strong acceleration at the start ofthe crosslinking but leads to a soft and tacky, and thereforeincompletely crosslinked, elastomer; the addition of free water and asimultaneous increase in the concentration of catalyst lead to the sameresult.

Moreover, it was observed that the elastomers obtained fromrapid-crosslinking silicone systems generally have a poorer adhesionthan that of the elastomers arising from slow-crosslinking siliconesystems. It is also known that tin-based catalysts are generallyunstable in the presence of water.

It was proposed (U.S. Pat. No. 4,918,140) to accelerate neutral(ketiminoxy) silicone compositions by addition, to a part (A) containingthe silicones to be crosslinked, of a part (B) containing awater-swollen organic polymer hydrogel; such a mixture must be carefullyhomogenized, as only the part (A) is capable of crosslinking whenexposed to atmospheric moisture; moreover, the final material is tackyas it is insufficiently crosslinked.

The Applicant company has now found an accelerator system for the coldcrosslinking of polymers which harden on exposure to moisture,especially neutral silicone elastomer compositions, the said systembeing stable with time and making it possible to obtain mastics oradhesives having an adhesion similar to that of slow-crosslinkingneutral silicone elastomer compositions.

The said accelerator system can also be used to accelerate the hardeningof polyesters or of polyethers containing alkoxysilane functional groupsor of polyurethanes.

The said accelerator system for the cold crosslinking of polymers whichharden on exposure to moisture by hydrolysis/condensation ischaracterized in that it comprises:

(C) x parts by weight of a catalyst for crosslinking the said polymersby polycondensation, x ranging from 0.01 to 10 and preferably from 0.1to 5;

(E) Y parts by weight of at least one solid inorganic compoundcontaining an amount y of water in the form of water of hydration and/orwater adsorbed by capillary condensation, this amount y ranging from 0.5to 40 parts by weight, preferably from 3 to 20 parts by weight, andwhich can represent up to 70% of the weight of the said solid inorganiccompound;

(F) z parts by weight of fillers, z ranging from 0 to 50 and preferablyfrom 1 to 30;

(D) 100-(x+Y+z) parts by weight of a diluent or of a solvent of the saidcatalyst (C), the diluent or solvent having a dynamic viscosity at 25°C. of the order of 50 to 200,000 mPa.s.;

the respective amounts of the four constituents (C), (E), (F) and (D)being such that the system obtained exists in the form of a manipulablepaste.

Mention may be made, among crosslinking catalysts (C) which can be used,of those based on tin, titanium, zirconium, manganese, lead and the likesuch as:

organotin salts of carboxylic acids such as tin 2-ethylhexanoate,dibutyltin diacetate, dibutyltin dilaurate and the like (some of thesecatalysts are described in the work by Noll entitled "Chemistry andTechnology of Silicones", page 397, 2nd paragraph--Academic Press, 1968)

reaction products of organotin salts of carboxylic acids with titanicesters (U.S. Pat. No. 3,403,753)

tin chelates (Patent EP-B-147,323)

organic derivatives of titanium and of zirconium, such as titanic andzirconic esters (U.S. Pat. No. 4,525,565)

tin, zinc or lead octoates.

Mention may be made, among solid inorganic compounds (E) which cancontain up to 70% of their weight of water of hydration and/or wateradsorbed by capillary condensation, of:

hydrated crystalline alkali metal or alkaline-earth metalaluminosilicates (also known as zeolites and molecular sieves); theseexist in the form of a crystal lattice containing interconnectedcavities of uniform opening, forming pores capable of adsorbingsignificant amounts of water; mention may especially be made of zeolites4A containing from 4 to 22% by weight of water;

hydrated silica gels; these have a microporous structure which canretain significant amounts of water (for example up to 22% by weight) bycapillary condensation;

hydrated inorganic salts containing water of crystallization, such asespecially borates, phosphates, carbonates and the like of alkali metalsor alkaline-earth metals such as sodium, calcium, magnesium or barium;mention may be made of Na₂ B₄ O₇.10H₂ O containing 47% by weight ofwater, Na₂ HPO₄.12H₂ O containing 60% by weight of water or Na₂ CO₃.10H₂O containing 63% of water;

and the like.

Mention may be made, among diluents or solvents (D) of the saidcrosslinking catalyst (C), of

α,ω-bis(triorganosiloxy)polydiorganosiloxanes formed essentially fromdiorganosiloxy units and from at least 1% by weight of monoorganosiloxyand/or siloxy units, the organic radicals bonded to the silicon atomsbeing chosen from C₁ -C₈ alkyl, vinyl or phenyl radicals, at least 40%by weight of these radicals being methyl radicals and at most 10% beingvinyl radicals;

optionally halogenated aromatic, cycloaliphatic or aliphatichydrocarbons, such as n-heptane, n-octane, cyclohexane,methylcyclohexane, toluene, xylene, mesitylene, cumene, tetralin,perchloroethylene, trichloroethane, tetrachloroethane, chlorobenzene,ortho-dichlorobenzene and the like;

aliphatic and cycloaliphatic ketones such as methyl ethyl ketone, methylisobutyl ketone, cyclohexanone, isophorone and the like;

esters such as ethyl acetate, butyl acetate, ethylene glycol acetate andthe like.

The fillers (F) can be organic in nature (poly(vinyl chloride) powder,polyethylene powder and the like) or preferably inorganic in nature.

These inorganic fillers can exist in the form of very finely dividedproducts, with a mean diameter of less than 0.1 μm, such as combustionor precipitation silicates with a specific surface generally greaterthan 40 m² /g, or in the form of coarsely divided products, with a meandiameter greater than 0.1 μm, such as ground quartz, diatomaceoussilicas, calcium carbonate, calcined clay, carbon black, titanium oxideof rutile type, iron, zinc, chromium, zirconium or magnesium oxides, thevarious forms of alumina, boron nitride, lithopone or barium metaborate,with a specific surface generally less than 30 m² /g; they canoptionally be surface modified by the various silicon compounds normallyused for this purpose (organochlorosilanes, organopolysiloxanes,organopolysilazanes and the like mentioned in FR-A-1,126,884,FR-A-1,136,885, FR-A-1,236,505 or GB-A-1,024,234).

Although containing hydrolysable catalysts (tin or titanium salts andthe like), it was observed that the accelerator system forming thesubject of the invention is stable with time.

The latter is very particularly advantageous for accelerating siliconecompositions which harden on exposure to the moisture in air, comprisingby weight:

(H) 100 parts of an α,ω-di(hydroxy)diorganopolysiloxane, with a dynamicviscosity of the order of 500 to 500,000 mPa.s at 25° C., preferably ofthe order of 3000 to 200,000 mPa.s, consisting of a sequence ofdiorganopolysiloxy units of formula R₂ SiO, in which formula the Rsymbols, which are identical or different, represent alkyl, alkenyl oraryl radicals containing from 1 to 8 carbon atoms, at least 80% bynumber of the said radicals preferably being methyl radicals;

(R) from 2 to 10 parts by weight, preferably from 4 to 8 parts byweight, of at least one crosslinking agent RSiX₃ or SiX₄, where R hasthe definition given above and X represents a hydrolysable group;

(C') from 0.005 to 0.5 part by weight, preferably from 0.01 to 0.1 partby weight, of a catalyst for crosslinking by polycondensation;

(F') from 0 to 200 parts by weight, preferably from 3 to 100 parts byweight, of fillers.

The α,ω-di(hydroxy)diorganopolysiloxanes (H) are essentially linearproducts; they can, however, comprise up to 2% by number of RSiO₁.5and/or SiO₂ units with respect to the number of diorganosiloxy units.The dynamic viscosities mentioned above are measured at 25° C. using aBrookfield viscometer according to AFNOR Standard NFT 76 102 of February1972.

Mention my be made, among the hydrocarbon radicals R, of the radicals:

methyl, ethyl, propyl, 3,3,3-trifluoropropyl, cyclohexyl, cyanoethyl andthe like

vinyl, allyl, butenyl and the like

phenyl, chlorophenyl and the like.

It must be understood, according to a variant of the invention, thatcopolymers or a mixture consisting of a number of polymers which differfrom each other in molecular weight and/or the nature of the radicalsbonded to the silicon can also be used as polymer (H).

The crosslinking agent (R) has at least one hydrolysable group such as:

acyloxy of formula --O--CO--R'

alkoxy of formula --O--R'

amino of formula --NR¹ R²

amido of formula --NR¹ COR²

alkenyloxy of formula --O--CR¹ ═CHR²

aminoxy of formula --O--NR¹ R²

ketiminoxy of formula ##STR1## where R' represents an alkyl or arylradical having from 1 to 15 carbon atoms, R¹ and R², which are identicalor different, represent alkyl or aryl radicals containing from 1 to 8carbon atoms and T an alkylene radical containing from 4 to 8 carbonatoms. Mention may very particularly be made, among the radicals R', R¹and R², of the methyl, ethyl, ayclohexyl or phenyl radicals and thelike.

Mention may very particularly be made, among the radicals T, of those offormula --(CH₂)₄ -, --(CH2)₅ -, --(CH₂)₆ - and the like.

The crosslinking agents preferentially used are alkoxysilanes andketiminoxysilanes.

Mention may be made, as examples of alkoxysilanes, of those of formula##STR2##

Mention may be made, as examples of ketiminoxysilanes, of those offormula ##STR3##

The acyloxysilane crosslinking agents are also advantageous.

Mention may be made, as examples of acyloxysilanes, of those of formula##STR4##

The catalyst (C') which can be used has the same definition as that ofthe catalyst (C) present in the accelerator system. The said catalysts(C) and (C') can be identical or different.

According to a variant of the invention, the said catalyst (C') can beomitted from the silicone composition as defined above whenhomogenization of the said composition is sufficient; the amount ofcatalyst (C) in the accelerator system must then compensate for the lackof catalyst (C').

The fillers (F') which can be used have the same definition as thosepresent in the accelerator system; they can be identical or different.

For a good implementation of the invention, the amount of acceleratorsystem to be introduced into the silicone composition which crosslinkswhile cold is such that the amount of water present in the finalcomposition is of the order of 0.1 to 4%, preferably of 0.3 to 2%, byweight.

The viscosity and the amount of diluent or solvent (D) in theaccelerator system is a function of the nature and of the level of theinorganic filler (F) which it optionally contains, as well as of theviscosity of the silicone composition to be accelerated. The presence orabsence of fillers (F) and the choice of these fillers is also afunction of the viscosity of the silicone composition to be accelerated.For a good implementation of the invention, it is recommended to use anaccelerator system whose dynamic viscosity at 25° C. is in the region ofthat of the silicone composition to be accelerated.

The use of the said accelerator system in silicone compositions whichharden on exposure to the moisture in air makes it possible to obtainmastics or adhesives which set satisfactorily rapid even throughout thethickness, and which have good adhesion.

The silicone compositions which harden on exposure to the moisture inair described above can additionally contain conventional additiveadjuvants, in particular

thermal stabilizing agents (in particular ceric oxides and hydroxides)in a proportion of 0.1 to 12 parts per 100 parts ofα,ω-di(hydroxy)diorganopolysiloxane (H);

compounds which improve fire resistance (in particular organic andinorganic platinum derivatives);

silicone plasticizers such asα,ω-bis(triorganosiloxy)polydiorganosiloxanes, with a dynamic viscosityof at least 10 mPa.s at 25° C., preferably of 10 to 1000 mPa.s at 25°C., formed essentially from diorganosiloxy units and from at most 1% byweight of monoorganosiloxy and/or siloxy units, the organic radicalsbonded to the silicon atoms being chosen from methyl, vinyl or phenylradicals, at least 40% by weight of these radicals being methyl radicalsand at most 10% being vinyl radicals; they are used in a proportion of 5to 120 parts by weight per 100 parts ofα,ω-di(hydroxy)diorganopolysiloxane (H);

organic plasticizers such as the products from the alkylation of benzenewith long-chain olefins, with a molecular weight greater than 200, in aproportion of 0 to 50 parts by weight per 100 parts ofα,ω-di(hydroxy)diorganopolysiloxane (H);

compounds contributing thixotropic properties such as

liquid branched methylpolysiloxane polymers having from 1.4 to 1.9methyl radicals per silicon atom and consisting of a combination ofunits of formula (CH₃)₃ SiO_(1/2), (CH₃)₂ SiO and CH₃ SiO_(3/2) ; theycontain from 0.1 to 8% of hydroxyl groups; they can be obtained byhydrolysis of the corresponding chlorosilanes; they are introduced in aproportion of 3 to 50 parts by weight per 100 parts ofα,ω-di(hydroxy)diorganopolysiloxane (H);

hydroxylated silicon compounds which are solid at room temperature suchas diphenylsilanediol, dimethylphenylsilanediol and the like; they areused in a proportion of 0.5 to 20 parts by weight per 100 parts ofα,ω-di(hydroxy)diorganopolysiloxane (H);

oils which make it possible to reduce the overall viscosity such asα,ω-di(hydroxy)dimethylphenylpolysiloxane oils with a dynamic viscosityof the order of 200 to 600 mPa.s or α,ω-di(methoxy)- or-di(ethoxy)dimethylpolysiloxane oils with a dynamic viscosity of theorder of 30 to 2000 mPa.s; they are used in a proportion of 2 to 40parts by weight per 100 parts of α,ω-di(hydroxy)diorganopolysiloxane(H);

The adhesion to various substrates, such as wood, aluminium, concrete,PVC and the like, of the elastomer formed by hardening the siliconecompositions described above can be further improved by addition, per100 parts of the said composition, of 0.1 to 5 parts of at least oneadhesion agent such as

C₁ -C₁₀ alkyl polysilicates (ethyl or methyl polysilicate)

alkoxysilanes of formula Z_(n) Si (OZ')_(4-n) where

Z is a saturated or unsaturated C_(1-C) ₁₀ hydrocarbon radicaloptionally containing nitrogen as a heteroatom

Z' is a C₁ -C₈ alkyl radical or a C₃ -C₆ alkoxyalkylene. radical

n is equal to 0 or 1.

Mention may be made, by way of examples, of alkoxysilanes,vinylalkoxysilanes, (Δ² -imidazolinyl) alkoxysilanes andaminoalkoxysilanes:

vinyltrimethoxysilane

vinyltris (methoxyethoxy) silane

tetra (methoxyethoxy) silane ##STR5##

    (C.sub.2 H.sub.5 O).sub.3 Si(CH.sub.2).sub.3 NCH.sub.2 CH.sub.2 N═CH

    (C.sub.2 H.sub.5 O).sub.3 Si(CH.sub.2).sub.3 NH.sub.2

    CH.sub.3 (C.sub.2 H.sub.5 O).sub.2 Si(CH.sub.2).sub.3 NH.sub.2

    (CH.sub.30).sub.3 Si(CH.sub.2).sub.3 NH(CH.sub.2).sub.2 NH.sub.2

The silicone compositions which harden on exposure to the moisture inair and which contain the said accelerator system which forms thesubject of the invention are prepared by simple mixing of theaccelerator system with the other constituents of the composition, forexample by manual mixing or using a static mixer or a pump or from atwo-component cartridge equipped with a static mixer.

The said rapid-hardening compositions can be used in many applicationssuch as pointing in the building industry, joining materials, insulatingelectrical conductors, coating electronic circuits or preparing mouldswhich are used in the manufacture of objects made of resin or syntheticfoam. They are very particularly advantageous for any application whichrequires a rapid setting in thickness such as in the production ofseals, especially of "in situ" seals used in the automobile industry("flattened", "shaped" or "injected" seals) or in the manufacture ofdouble glazings, of bonded external glazings or of seals for domesticelectrical appliances.

Complete crosslinking after addition of the accelerator system requiresapproximately 1 to 24 hours.

The following examples are given by way of illustration and cannot beregarded as limiting the sphere or spirit of the invention.

EXAMPLES 1 TO 15

An accelerator system for crosslinking while cold is prepared bydispersion, in a silicone oil, of the solid inorganic compound (E)containing water in the form of water of hydration and/or water adsorbedby capillary condensation, addition of the optional fillers (silica,calcium carbonate) and then the tin catalyst, and mixing.

A pasty liquid accelerator system is thus obtained. The nature and theamounts of the various constituents of the accelerator system appear inTables 1 and 2. In these tables, the various abbreviations ordesignations have the following meaning:

12% MS: zeolite 4A powder containing 12% by weight of water

22% MS: zeolite 4A powder containing 22% by weight of water

silica gel: activated standard Levilite® marketed by Rhone-Poulenc

Aqua Keep®: Aqua Keep®X5 T-S (alkali metal polyacrylate marketed byNorsolor, forming a hydrogel by addition of water)

47 V 30,000: polydimethylsiloxane oil with a dynamic viscosity at 25° C.of the order of 30,000 mPa.s

47 V 100: polydimethylsiloxane oil with a dynamic viscosity at 25° C. ofthe order of 100 mPa.s

48 V 3500: α,ω-di(hydroxy)polydimethylsiloxane oil with a dynamicviscosity at 25° C. of the order of 3500 mPa.s

silica: Aerosil®150 silica with a BET surface of 150 m² /g, marketed byDegussa

DOctSnDL: dioctyltin dilaurate, Metatin® 812 marketed by Acima

DBuSnDL: dibutyltin dilaurate, Metatin® 712 E marketed by Acima.

The performances of the accelerator systems prepared above are tested inthe presence of elastomer compositions capable of crosslinking whilecold in the presence of moisture, in a proportion of 10 parts by weightof accelerator system per 100 parts of elastomer composition.

The accelerator systems of Examples 1 to 9 were tested in the presenceof the elastomer composition CAF Rhodorseal®5942 marketed byRhone-Poulenc, which composition is based on anα,ω-di(hydroxy)polydimethylsiloxane oil with a dynamic viscosity of 25°C. of the order of 70,000 mPa.s, on a crosslinking alkoxysilane, onaminated silanes as adhesion agents, on calcium carbonate, on silica andon a tin catalyst.

The accelerator systems of Examples 10 to 12 were tested in the presenceof the elastomer composition Mastic Rhodorsil® 6B, marketed byRhone-Poulenc, which composition is based on anα,ω-di(hydroxy)polydimethylsiloxane oil with a dynamic viscosity at 25°C. of the order of 70,000 mPa.s, on crosslinking ketiminoxysilanes, onaminated silanes as adhesion agents, on silica and on a tin catalyst.

The accelerator system of Example 3, after storing for 18 months, andthat of Example 13 were tested in the presence of the elastomercomposition Mastic Rhodorsil® N8, marketed by Rhone-Poulenc, whichcomposition is based on an α,ω-di(hydroxy)polydimethylsiloxane oil witha dynamic viscosity at 25° C. of the order of 50,000 mPa.s, oncrosslinking ketiminoxysilanes, on aminated silanes as adhesion agents,on silica and on a tin catalyst.

The accelerator system of Example 14 was tested in the presence of theelastomer composition CAF Rhodorseal® 5761, marketed by Rhone-Poulenc,which composition is based on an α,ω-di(hydroxy)polydimethylsiloxane oilwith a dynamic viscosity at 25° C. of the order of 3500 mPa.s, oncrosslinking acetoxysilanes, on silica and on a titanium catalyst.

The accelerator system of Example 15 was tested in the presence of theelastomer composition Mastic Rhodorseal® 3B, marketed by Rhone-Poulenc,which composition is based on an α,ω-di(hydroxy)polydimethylsiloxane oilwith a dynamic viscosity of 25° C. of the order of 70,000 mPa.s, oncrosslinking acetoxysilanes, on silica and on a titanium catalyst. Therate of crosslinking of the elastomer composition in the presence of theaccelerator system is estimated according to at least one of the threefollowing methods:

by measuring the time required for demoulding a thick seal with athickness of 10 mm or 6 mm;

by monitoring the change with time of the Shore A hardness (ASTM D 2240or ISO R 868 Standard) on the two faces (face in contact with air andenclosed face) of a seal with a thickness of 10 mm;

using a vibrating needle Rapra® curometer marketed by Rapra TechnologyLtd., which measures the attenuation in the vibrational amplitude of theneedle due to the increases in viscosity and elastic modulus of theelastomer during its crosslinking (the steel needle is immersed in theformulation, the immersed length of the needle being approximately 5 mm,and is then driven by a vertical vibrational movement transmitted by anelectrodynamic vibrator; the resistance to movement measured during thecrosslinking of the elastomer is expressed in mV); and compared withthat of the elastomer composition which is free of the said acceleratorsystem (termed "control").

Time required for demoulding

It is observed that the time required for demoulding the elastomercomposition:

CAF Rhodorseal® 5942, "control", is 240 h for a seal with a thickness of10 mm;

CAF Rhodorseal® 5942, accelerated by the system of Example 1, is 24 hfor a seal with a thickness of 10 mm;

CAF Rhodorseal® 5942, accelerated by the system of Example 5 or 6, isless than 24 h for a seal with a thickness of 10 mm;

CAF Rhodorseal® 5761, "control", is 130 h for a seal with a thickness of10 mm;

CAF Rhodorseal® 5761, accelerated by the system of Example 14, is 6 hfor a seal with a thickness of 10 mm; the Shore A hardness is 44 (airface) and 43 (enclosed face);

Mastic Rhodorsil® 3B, "control", is 40 h for a seal with a thickness of6 mm;

Mastic Rhodorsil® 3B, accelerated by the system of Example 15, is 15 hfor a seal with a thickness of 6 mm.

Development of the hardness

The appended FIGS. 1 to 10 represent the development of the hardness ofthe chosen elastomer composition accelerated by a system of Examples 1to 9, according to the following correlation:

    ______________________________________                                                                      Accelerator                                     FIG.     Elastomer composition                                                                              system of                                       ______________________________________                                        FIG. 1   CAF Rhodorseal ®, 5942, "control"                                FIG. 2   CAF Rhodorseal ® 5942                                                                          Example 1                                       FIG. 3   CAF Rhodorseal ® 5942                                                                          Example 5                                       FIG. 4   CAF Rhodorseal ® 5942                                                                          Example 6                                       FIG. 5   CAF Rhodorseal ® 5942                                                                          Example 8*                                                                    (free water)                                    (crosslinking is accelerated but the final product remains tacky              and soft)                                                                     FIG. 6   CAF Rhodorseal ® 5942                                                                          Example 9*                                                                    (free water +                                                                 cata.)                                          (the final elastomer remains tacky and soft; the hardness                     remains well below that of the "control" elastomer)                           FIG. 7   Mastic Rhodorsil ® 6B, "control"                                          Mastic Rhodorsil ® 6B                                                                          Example 10                                               Mastic Rhodorsil ® 6B                                                                          Example 11*                                                                   (without cata.)                                 FIG. 8   Mastic Rhodorsil ® 6B                                                                          Example 10                                               Mastic Rhodorsil ® 6B                                                                          Example 12*                                                                   (hydrogel +                                                                   cata.)                                          FIG. 9   Mastic Rhodorsil ® N8                                                                          Example 13                                      FIG. 10  Mastic Rhodorsil ® N8                                                                          Example 3                                                                     after storing                                                                 for 8 months                                    ______________________________________                                    

Measurement with the curometer

The appended FIGS. 11 to 19 represent the development in the resistanceto movement of the chosen elastomer composition accelerated by a systemof Examples 2 to 12, according to the following correlation:

    ______________________________________                                                                      Accelerator                                     FIG.     Elastomer composition                                                                              System of                                       ______________________________________                                        FIG. 11-12                                                                             CAF Rhodorseal ® 5942, "control"                                 FIG. 13  CAP Rhodorseal ® 5942                                                                          Example 2                                       FIG. 14  CAF Rhodorseal ® 5942                                                                          Example 3                                       FIG. 15  CAF Rhodorseal ® 5942                                                                          Example 4                                       FIG. 16  CAF Rhodorseal ® 5942                                                                          Example 7*                                                                    (without E)                                     (no acceleration is observed with respect to the control)                     FIG. 17  CAP Rhodorseal ® 5942                                                                          Example 1                                       FIG. 18  Mastic Rhodorsil ® 6B, "control"                                          Mastic Rhodorsil ® 6B                                                                          Example 10                                               Mastic Rhodorsil ® 6B                                                                          Example 11*                                                                   (without cata.)                                 FIG. 19  Mastic Rhodorsil ® 6B                                                                          Example 10                                               Mastic Rhodorsil ® 6B                                                                          Example 12*                                                                   (hydrogel +                                                                   cata.)                                          ______________________________________                                    

Measurements carried out using the same accelerator systems stored foreight months give results which are not significantly different fromthose obtained using the fresh systems.

                  TABLE 1                                                         ______________________________________                                                  Example                                                                       1    2     3      4   5   6    7*  8*  9*                           ______________________________________                                        Inorganic compound E                                                          (% by weight)                                                                 Na.sub.2 B.sub.4 O.sub.7 10H.sub.2 O                                                      15                                                                12% MS             36                                                         22% MS                   31                                                   silica gel                    31                                              Na.sub.2 HPO.sub.4.12H.sub.2 O    11                                          Na.sub.2 CO.sub.3.10H.sub.2 O         10.5                                    Free water                                     7   7                          (% by weight)                                                                 Silicone diluent                                                              (% by weight)                                                                 47 V 30,000 47                    86  86.5 97  89  88                         47 V 100           61    66   66                                              48 V 3500                                                                     Silica (% by weight)                                                                      2      2     2    2   2   2    2   4   4                          Ca carbonate                                                                              35                                                                (% by weight)                                                                 Catalyst                                                                      (% by weight)                                                                 DOctSnDL    1      1     1    1   1   1    1   0   1                          ______________________________________                                         *comparative examples                                                    

                  TABLE 2                                                         ______________________________________                                                  Example                                                                       10   11*     12*    13   14    15                                   ______________________________________                                        Inorganic compound E                                                          (% by weight)                                                                 Na.sub.2 B.sub.4 O.sub.7.10H.sub.2 O                                                                          15   14.8  21                                 12% MS                                                                        22% MS      32     32                                                         silica gel                                                                    Na.sub.2 HPO.sub.4.12H.sub.2 O                                                Na.sub.2 CO.sub.3.10H.sub.2 O                                                 Aqua Keep ®            0.1                                                (% by weight)                                                                 Free Water                 7                                                  (% by weight)                                                                 Silicone diluent                                                              (% by weight)                                                                 47 V 30,000                87.9      82.9  76.3                               47 V 100                                                                      48 V 3500   65     68           82                                            Silica (% by weight)                                                                             4                 2.5   2.5                                Catalyst                                                                      (% by weight)                                                                 DOctSnDL    3      0       1                                                  DBuSnDL                         3    0.8                                      Bu titanate                                0.2                                ______________________________________                                         *comparative examples                                                    

We claim:
 1. A silicone/accelerator system composition comprising anaccelerator system and a silicone composition which hardens on exposureto the moisture in air, said accelerator system comprising in parts byweight:(C) x parts by weight of a catalyst for crosslinking the saidpolymers by polycondensation, x ranging from 0.01 to 10; (E) Y parts byweight of at least one solid inorganic compound containing an amount yof water in the form of water of hydration and/or water adsorbed bycapillary condensation, the amount y ranging from 0.5 to 40 parts byweight of said accelerator system, and the amount y representing up to70% of the weight of said solid inorganic compound; (F) z parts byweight of fillers, z ranging from 0 to 50; (D) 100-(x+Y+z) parts byweight of a diluent or of a solvent of the said catalyst (C), thediluent or solvent having a dynamic viscosity at 25° C. of about 50 toabout 200,000 mPa.s; the respective amounts of the four constituents(C), (E), (F) and (D) being such that the accelerator system obtainedexists in the form of a manipulable paste; and said silicone compositioncomprising in parts by weight: (H) 100 parts of anα,ω-di-(hydroxy)-diorganopolysiloxane, with a dynamic viscosity of about500 to about 500,000 mPa.s at 25° C., consisting of a sequence ofdiorganopolysiloxy units of formula R₂ SiO, in which formula the Rsymbols, which are identical or different, represent alkyl, alkenyl oraryl radicals containing from 1 to 8 carbon atoms; (R) from 2 to 10parts by weight of at least one crosslinking agent RSiX₃ or SiX₄, whereR has the definition given above and X represents a hydrolyzable group;(C') from 0.005 to 0.5 part by weight of a catalyst for crosslinking bypolycondensation; (F') from 0 to 200 parts by weight of fillers.
 2. Thesilicone/accelerator system composition according to claim 1, whereinmethyl radicals constitute at least 80% by number of said alkyl, alkenyland aryl radicals of said α,ω-di-(hydroxy)-diorganopolysiloxane (H) orsaid crosslinking agent (R).
 3. The silicone/accelerator systemcomposition according to claim 1, wherein the crosslinking agent (R) isalkoxysilane or ketiminoxysilane.
 4. The silicone/accelerator systemcomposition according to claim 1, wherein the amount of water present inthe final silicone/accelerator system composition is about 0.1 to about4% by weight.
 5. The silicone/accelerator system composition accordingto claim 1, wherein x ranges from 0.1 to 5; y ranges from 3 to 20; and zranges from 1 to
 30. 6. The silicone/accelerator system compositionaccording to claim 1, wherein the catalyst (C) is based on tin,titanium, zirconium, manganese or lead.
 7. The silicone/acceleratorsystem composition according to claim 1, wherein said solid inorganiccompound (E) is a hydrated crystalline alkali metal or alkaline-earthmetal aluminosilicate, a hydrated silica gel or a hydrated inorganicsalt containing water of crystallization.
 8. The silicone/acceleratorsystem composition according to claim 7, wherein said solid inorganiccompound (E) is Na₂ B₄ O₇.10H₂ O containing 47% by weight of water, Na₂HPO₄.12H₂ O containing 60% by weight of water or Na₂ CO₃.10H₂ Ocontaining 63% of water.
 9. The silicone/accelerator system compositionaccording to claim 1, wherein said diluent or solvent (D) is selectedfrom the group consisting ofα,ω-bis(triorganosiloxy)polydiorgano-siloxanes, aromatic hydrocarbons,cycloaliphatic hydrocarbons, aliphatic hydrocarbons, halogenatedaromatic hydrocarbons, halogenated cycloaliphatic hydrocarbons,halogenated aliphatic hydrocarbons, ketones, cycloaliphatic ketones, andesters.
 10. The silicone/accelerator system composition according toclaim 1, wherein said filler (F) is silica.